Clinical challenges treating Stenotrophomonas maltophilia infections: an update

Clinical characteristics and genome epidemiology of Stenotrophomonas maltophilia in Japan

BACKGROUND

Stenotrophomonas maltophilia is a carbapenem-resistant Gram-negative pathogen increasingly responsible for difficult-to-treat nosocomial infections.

OBJECTIVES

To describe the contemporary clinical characteristics and genome epidemiology of patients colonized or infected by S. maltophilia in a multicentre, prospective cohort.

METHODS

All patients with a clinical culture growing S. maltophilia were enrolled at six tertiary hospitals across Japan between April 2019 and March 2022. The clinical characteristics, outcomes, antimicrobial susceptibility and genomic epidemiology of cases with S. maltophilia were investigated.

RESULTS

In total, 78 patients were included representing 34 infection and 44 colonization cases. The median age was 72.5 years (IQR, 61-78), and males accounted for 53 cases (68%). The most common comorbidity was localized solid malignancy (39%). Nearly half of the patients (44%) were immunosuppressed, with antineoplastic chemotherapy accounting for 31%. The respiratory tract was the most common site of colonization (86%), whereas bacteraemia accounted for most infection cases (56%). The 30 day all-cause mortality rate was 21%, which was significantly higher in infection cases than colonization cases (35% versus 9%; adjusted HR, 3.81; 95% CI, 1.22-11.96). Susceptibility rates to ceftazidime, levofloxacin, minocycline and sulfamethoxazole/trimethoprim were 14%, 65%, 87% and 100%, respectively. The percentage of infection ranged from 13% in the unclassified group to 86% in genomic group 6A. The percentage of non-susceptibility to ceftazidime ranged from 33% in genomic group C to 100% in genomic groups 6 and 7 and genomic group geniculate.

CONCLUSIONS

In this contemporary multicentre cohort, S. maltophilia primarily colonized the respiratory tract, whereas patients with bacteraemia had the highest the mortality from this pathogen. Sulfamethoxazole/trimethoprim remained consistently active, but susceptibility to levofloxacin was relatively low. The proportions of cases representing infection and susceptibility to ceftazidime differed significantly based on genomic groups.

Biofilm Eradication of Stenotrophomonas maltophilia by Levofloxacin and Trimethoprim-Sulfamethoxazole

Stenotrophomonas maltophilia is a nonfermenting Gram-negative drug-resistant pathogen that causes healthcare-associated infections. Clinical isolates from Mexico were assessed for biofilm formation using crystal violet staining. Antimicrobial susceptibility was evaluated in planktonic and biofilm cells using the broth microdilution method. The effects of antibiotics on biofilms were visualized using fluorescence microscopy. Fifty isolates were included in this study, of which 14 (28%) were biofilm producers (9 [64%] from blood and 5 [36%] from respiratory samples). In planktonic cells 4/50 (8%) of isolates were resistant to levofloxacin (8.0%) and 22/50 (44%) were resistant to trimethoprim-sulfamethoxazole. All isolates were resistant to levofloxacin and trimethoprim-sulfamethoxazole in biofilm cells. Bacterial biofilms treated with different concentrations of both antibiotics were completely disrupted. In conclusion, S. maltophilia isolated from blood had higher biofilm production than those isolated from respiratory samples. Biofilm production was associated with increased antibiotic resistance. Antibiotic monotherapy might not be the best course of action for the treatment of S. maltophilia infections in Mexico, because it might cause biofilm production and antimicrobial resistance.

Drug Resistance in Biofilm and Planktonic Cells of Achromobacter spp., Burkholderia spp., and Stenotrophomonas maltophilia Clinical Isolates

Background: Biofilm production in nonfermenting Gram-negative bacteria influences drug resistance. The aim of this work was to evaluate the effect of different antibiotics on biofilm eradication of clinical isolates of Achromobacter, Burkholderia, and Stenotrophomonas maltophilia. Methods: Clinical isolates were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry in a third-level hospital in Monterrey, Mexico. Crystal violet staining was used to determine biofilm production. Drug susceptibility testing was determined by broth microdilution in planktonic cells and biofilm cells. Results: Resistance in planktonic cells was moderate to trimethoprim-sulfamethoxazole, and low to chloramphenicol, minocycline, levofloxacin (S. maltophilia and Burkholderia), ceftazidime, and meropenem (Burkholderia and Achromobacter). Biofilm eradication required higher drug concentrations of ceftazidime, chloramphenicol, levofloxacin, and trimethoprim-sulfamethoxazole than planktonic cells (p < 0.05). Levofloxacin showed biofilm eradication activity in S. maltophilia, minocycline and meropenem in Burkholderia, and meropenem in Achromobacter. Conclusions: Drug resistance increased due to biofilm production for some antibiotics, particularly ceftazidime and trimethoprim-sulfamethoxazole for all three pathogens, chloramphenicol for S. maltophilia and Burkholderia, and levofloxacin for Burkholderia. Some antibiotics could be used for the treatment of biofilm-associated infections in our population, such as levofloxacin for S. maltophilia, minocycline and meropenem for Burkholderia, and meropenem for Achromobacter.

Bactericidal effectors of the Stenotrophomonas maltophilia type IV secretion system: functional definition of the nuclease TfdA and structural determination of TfcB

Stenotrophomonas maltophilia expresses a type IV protein secretion system (T4SS) that promotes contact-dependent killing of other bacteria and does so partly by secreting the effector TfcB. Here, we report the structure of TfcB, comprising an N-terminal domain similar to the catalytic domain of glycosyl hydrolase (GH-19) chitinases and a C-terminal domain for recognition and translocation by the T4SS. Utilizing a two-hybrid assay to measure effector interactions with the T4SS coupling protein VirD4, we documented the existence of five more T4SS substrates. One of these was protein 20845, an annotated nuclease. A S. maltophilia mutant lacking the gene for 20845 was impaired for killing Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Moreover, the cloned 20845 gene conferred robust toxicity, with the recombinant E. coli being rescued when 20845 was co-expressed with its cognate immunity protein. The 20845 effector was an 899 amino-acid protein, comprised of a GHH-nuclease domain in its N-terminus, a large central region of indeterminant function, and a C-terminus for secretion. Engineered variants of the 20845 gene that had mutations in the predicted catalytic site did not impede E. coli, indicating that the antibacterial effect of 20845 involves its nuclease activity. Using flow cytometry with DNA staining, we determined that 20845, but not its mutant variants, confers a loss in DNA content of target bacteria. Database searches revealed that uncharacterized homologs of 20845 occur within a range of bacteria. These data indicate that the S. maltophilia T4SS promotes interbacterial competition through the action of multiple toxic effectors, including a potent, novel DNase.IMPORTANCEStenotrophomonas maltophilia is a multi-drug-resistant, Gram-negative bacterium that is an emerging pathogen of humans. Patients with cystic fibrosis are particularly susceptible to S. maltophilia infection. In hospital water systems and various types of infections, S. maltophilia co-exists with other bacteria, including other pathogens such as Pseudomonas aeruginosa. We previously demonstrated that S. maltophilia has a functional VirB/D4 type VI protein secretion system (T4SS) that promotes contact-dependent killing of other bacteria. Since most work on antibacterial systems involves the type VI secretion system, this observation remains noteworthy. Moreover, S. maltophilia currently stands alone as a model for a human pathogen expressing an antibacterial T4SS. Using biochemical, genetic, and cell biological approaches, we now report both the discovery of a novel antibacterial nuclease (TfdA) and the first structural determination of a bactericidal T4SS effector (TfcB).

Clinical and microbiological features of positive blood culture episodes caused by non-fermenting gram-negative bacilli other than Pseudomonas and Acinetobacter species (2020-2023)

INTRODUCTION

Non-fermenting Gram-negative bacilli (NFGNB) other than Pseudomonas aeruginosa and Acinetobacter baumannii complex are pathogens of interest due to their ability to cause health-care associated infections and display complex drug resistance phenotypes. However, their clinical and microbiological landscape is still poorly characterized.

METHODS

Observational retrospective study including all hospitalized patients presenting with a positive positive blood culture (BC) episode caused by less common NFGNB over a four-year period (January 2020-December 2023). Clinical-microbiological features and factors associated with mortality were investigated.

RESULTS

Sixty-six less common NFGNB isolates other than Pseudomonas and Acinetobacter species causing 63 positive BC episodes were recovered from 60 patients. Positive BC episodes were predominantly sustained by Stenotrophomonas maltophilia (49.2%) followed by Achromobacter species (15.9%) that exhibited the most complex resistance phenotype. Positive BC episodes had bloodstream infection criteria in 95.2% of cases (60 out 63), being intravascular device (30.2%) and respiratory tract (19.1%) the main sources of infection. Fourteen-day, 30-day, and in-hospital mortality rates were 6.4%, 9.5%, and 15.9%, respectively. The longer time from admission to the positive BC episode, older age, diabetes, admission due to sepsis, and higher Charlson Comorbidity Index were identified as the main predictors of in-hospital mortality.

CONCLUSIONS

Positive BC episodes sustained by NFGNB other than Pseudomonas and Acinetobacter species were predominantly sustained by Stenotrophomonas maltophilia and Achromobacter species, having bloodstream infection criteria in the vast majority of cases. Factors that have emerged to be associated with mortality highlighted how these species may have more room in prolonged hospitalisation and at the end of life for patients with chronic organ diseases.

Temporal analysis of prevalence and antibiotic-resistance patterns in Stenotrophomonas maltophilia clinical isolates in a 19-year retrospective study

Stenotrophomonas maltophilia is a nonfermenting gram-negative bacterium associated with multiple nosocomial outbreaks. Antibiotic resistance increases healthcare costs, disease severity, and mortality. Multidrug-resistant infections (such as S. maltophilia infection) are difficult to treat with conventional antimicrobials. This study aimed to investigate the isolation rates, and resistance trends of S. maltophilia infections over the past 19 years, and provide future projections until 2030. In total, 4466 patients with S. maltophilia infection were identified. The adult and main surgical intensive care unit (ICU) had the highest numbers of patients (32.2%), followed by the cardiology department (29.8%), and the paediatric ICU (10%). The prevalence of S. maltophilia isolation increased from 7% [95% confidence interval (CI) 6.3-7.7%] in 2004-2007 to 15% [95% CI 10.7-19.9%] in 2020-2022. Most S. maltophilia isolates were resistant to ceftazidime (72.5%), levofloxacin (56%), and trimethoprim-sulfamethoxazole (14.05%), according to our study. A consistent and significant difference was found between S. maltophilia-positive ICU patients and non-ICU patients (P = 0.0017) during the three-year pandemic of COVID-19 (2019-2021). The prevalence of S. maltophilia isolates is expected to reach 15.08% [95% CI 12.58-17.59%] by 2030. Swift global action is needed to address this growing issue; healthcare authorities must set priorities and monitor infection escalations and treatment shortages.

Stenotrophomonas maltophilia: The Landscape in Critically Ill Patients and Optimising Management Approaches

The aim of this review is to synthesise the key aspects of the epidemiology, current microbiological diagnostic challenges, antibiotic resistance rates, optimal antimicrobial management, and most effective prevention strategies for Stenotrophomonas maltophilia (SM) in the intensive care unit (ICU) population. In recent years, resistance surveillance data indicate that SM accounts for less than 3% of all healthcare-associated infection strains, a percentage that doubles in the case of ventilator-associated pneumonia (VAP). Interestingly, SM ranks as the third most isolated non-glucose fermenter Gram-negative bacilli (NFGNB). Although this NFGNB genus has usually been considered a bystander and colonising strain, recently published data warn about its potential role as a causative pathogen of severe infections, particularly pneumonia and bloodstream infections (BSI), not only for the classical immunocompromised susceptible host patients but also for critically ill ones even without overt immunosuppression. Indeed, it has been associated with crude 28-day mortality as high as 54.8%, despite initial response following targeted therapy. Additionally, alongside its intrinsic resistance to a wide range of common antimicrobials, various worldwide and local surveillance studies raise concerns about an increase in ICU settings regarding resistance to first-line drugs such as cotrimoxazole or tigecycline. This scenario alerts ICU physicians to the need to reconsider the best stewardship approach when SM is isolated in obtained samples from critically ill patients. Despite the coverage of this multidrug-resistant bacterium (MDRB) provided by some traditional and a non-negligible number of current pipeline antimicrobials, an ecological and cost-effective strategy is needed in the present era.

Optimizing Antibiotic Therapy for Stenotrophomonas maltophilia Infections in Critically Ill Patients: A Pharmacokinetic/Pharmacodynamic Approach

Stenotrophomonas maltophilia is an opportunistic, multidrug-resistant non-fermentative Gram-negative bacillus, posing a significant challenge in clinical treatment due to its numerous intrinsic and acquired resistance mechanisms. This study aimed to evaluate the adequacy of antibiotics used for the treatment of S. maltophilia infections in critically ill patients using a pharmacokinetic/pharmacodynamic (PK/PD) approach. The antibiotics studied included cotrimoxazole, levofloxacin, minocycline, tigecycline, cefiderocol, and the new combination aztreonam/avibactam, which is not yet approved. By Monte Carlo simulations, the probability of target attainment (PTA), the PK/PD breakpoints, and the cumulative fraction of response (CFR) were estimated. PK parameters and MIC distributions were sourced from the literature, the European Committee on Antimicrobial Susceptibility Testing (EUCAST), and the SENTRY Antimicrobial Surveillance Program collection. Cefiderocol 2 g q8h, minocycline 200 mg q12h, tigecycline 100 mg q12h, and aztreonam/avibactam 1500/500 mg q6h were the best options to treat empirically infections due to S. maltophilia. Cotrimoxazole provided a higher probability of treatment success for the U.S. isolates than for European isolates. For all antibiotics, discrepancies between the PK/PD breakpoints and the clinical breakpoints defined by EUCAST (or the ECOFF) and CLSI were detected.

A novel pathogenic species of genus Stenotrophomonas: Stenotrophomonas pigmentata sp. nov

Introduction

Stenotrophomonas is a prominent genus owing to its dual nature. Species of this genus have many applications in industry and agriculture as plant growth-promoting rhizobacteria and microbial biological control agents, whereas species such as Stenotrophomonas maltophilia are considered one of the leading gram-negative multi-drug-resistant bacterial pathogens because of their high contribution to the increase in crude mortality and significant clinical challenge. Pathogenic Stenotrophomonas species and most clinical isolates belong to the Stenotrophomonas maltophilia complex (SMc). However, a strain highly homologous to S. terrae was isolated from a patient with pulmonary tuberculosis (TB), which aroused our interest, as S. terrae belongs to a relatively distant clade from SMc and there have been no human association reports.

Methods

The pathogenicity, immunological and biochemical characteristics of 610A2T were systematically evaluated.

Results

610A2T is a new species of genus Stenotrophomonas, which is named as Stenotrophomonas pigmentata sp. nov. for its obvious brown water-soluble pigment. 610A2T is pathogenic and caused significant weight loss, pulmonary congestion, and blood transmission in mice because it has multiple virulence factors, haemolysis, and strong biofilm formation abilities. In addition, the cytokine response induced by this strain was similar to that observed in patients with TB, and the strain was resistant to half of the anti-TB drugs.

Conclusions

The pathogenicity of 610A2T may not be weaker than that of S. maltophilia. Its isolation extended the opportunistic pathogenic species to all 3 major clades of the genus Stenotrophomonas, indicating that the clinical importance of species of Stenotrophomonas other than S. maltophilia and potential risks to biological safety associated with the use of Stenotrophomonas require more attention.

Multidrug-resistant Stenotrophomonas maltophilia in residential aged care facilities: An emerging threat

Stenotrophomonas maltophilia is a multidrug-resistant (MDR), Gram-negative bacterium intrinsically resistant to beta-lactams, including last-resort carbapenems. As an opportunistic pathogen, it can cause serious healthcare-related infections. This study assesses the prevalence, resistance profiles, and genetic diversity of S. maltophilia isolated from residential aged care facilities (RACFs). RACFs are known for their overuse and often inappropriate use of antibiotics, creating a strong selective environment that favors the development of bacterial resistance. The study was conducted on 73 S. maltophilia isolates recovered from wastewater and facility swab samples obtained from three RACFs and a retirement village. Phenotypic and genotypic assessments of the isolates revealed high carbapenem resistance, exemplifying their intrinsic beta-lactam resistance. Alarmingly, 49.3% (36/73) of the isolates were non-wild type for colistin, with minimum inhibitory concentration values of > 4 mg/L, and 11.0% (8/73) were resistant to trimethoprim-sulfamethoxazole. No resistance mechanisms were detected for either antimicrobial. Genotypic assessment of known lineages revealed isolates clustering with Sm17 and Sm18, lineages not previously reported in Australia, suggesting the potential ongoing spread of MDR S. maltophilia. Lastly, although only a few isolates were biocide tolerant (2.7%, 2/73), their ability to grow in high concentrations (64 mg/L) of triclosan is concerning, as it may be selecting for their survival and continued dissemination.

Hemorrhagic Pneumonia in a Kidney Transplant Recipient Caused by Stenotrophomonas Maltophilia Infection: A Case Report

Pneumonia is a common nosocomial complication in transplant patients. Stenotrophomonas maltophilia is recognized as a common cause and is typically seen in immunocompromised and critically ill patients. S. maltophilia, a nonfermenting gram-negative rod, ranks as the third most common nosocomial pathogen, following Pseudomonas aeruginosa and Acinetobacter. The bacteria are frequently found in environmental sources and are prevalent in healthcare facilities, including in tap water faucets, shower outlets, air-cooling systems, intravenous fluids, catheters, dialysis machines, and oxygen humidifiers. This bacterium possesses the ability to rapidly form biofilms, enabling it to colonize new surfaces in less than 24 hours. While S. maltophilia generally exhibits low virulence, there remains uncertainty among many clinicians regarding whether it is merely a colonizer or the primary cause of infection. Although S. maltophilia infections are rare in immunocompetent individuals, the species is increasingly recognized as an opportunistic pathogen in vulnerable populations such as those with cystic fibrosis, cancer, and other conditions leading to immunosuppression. S. maltophilia now recognized as a causative agent in various clinical syndromes, primarily affecting the lungs and bloodstream. We present a case of S. maltophilia-associated lung infection in a kidney transplant recipient, emphasizing the significance of underlying diseases and associated signs and symptoms.

Clonal spread of trimethoprim-sulfamethoxazole-resistant Stenotrophomonas maltophilia isolates in a tertiary hospital

Aim

The aims of this study were to: (i) determine antibiotic susceptibility of clinical Stenotrophomonas maltophilia isolates, (ii) investigate the presence of different classes of integrons and sul genes responsible for sulphonamide resistance, (iii) assess the molecular epidemiology of the isolates by determining their clonal relatedness, and (iv) investigate the potential sources of infection by collecting environmental samples when necessary.

Methods

99 S. maltophilia isolates from clinical specimens of hospitalized patients were screened by PCR for sul1, sul2, sul3 genes, and integron-associated integrase genes: intI1, intI2, and intI3. PFGE was used to determine the clonal relatedness of the isolates.

Results

Susceptibility rates for trimethoprim-sulfamethoxazole, levofloxacin, and ceftazidime were 90.9%, 91.9%, and 53.5% respectively. All trimethoprim-sulfamethoxazole-resistant isolates were positive for intI1 and sul1. PFGE analysis revealed that 24 of the isolates were clonally related, clustering in seven different clones. Five of the nine trimethoprim-sulfamethoxazole-resistant isolates were clonally related. The first isolate in this clone was from a wound sample of a patient in the infectious diseases clinic, and the other four were isolated from the bronchoalveolar lavage samples of patients in the thoracic surgery unit. The patient with the first isolate neither underwent bronchoscopy nor stayed in the thoracic surgery unit. Although clustering was observed in bronchoalveolar lavage samples, no S. maltophilia growth was detected in environmental samples.

Conclusion

The findings demonstrated that the sul1 gene carried by class 1 integrons plays an important role in trimethoprim-sulfamethoxazole resistance in S. maltophilia isolates. PFGE analysis revealed a high degree of genetic diversity. However, detection of clonally related isolates suggests the acquisition from a common source and/or cross-transmission of this microorganism between the patients.

Correlation between Stenotrophomonas maltophilia incidence and systemic antibiotic use: A 10-year retrospective, observational study in Hungary

Extensive use of carbapenems may lead to selection pressure for Stenotrophomonas maltophilia (SM) in hospital environments. The aim of our study was to assess the possible association between systemic antibiotic use and the incidence of SM. A retrospective, observational study was carried out in a tertiary-care hospital in Hungary, between January 1st 2010 and December 31st 2019. Incidence-density for SM and SM resistant to trimethoprim-sulfamethoxazole (SXT) was standardized for 1000 patient-days, while systemic antibiotic use was expressed as defined daily doses (DDDs) per 100 patient-days. Mean incidence density for SM infections was 0.42/1000 patient-days; 11.08% were were resistant to SXT, the mean incidence density for SXT-resistant SM was 0.047/1000 patient-days. Consumption rate for colistin, glycopeptides and carbapenems increased by 258.82, 278.94 and 372.72% from 2010 to 2019, respectively. Strong and significant positive correlations were observed with the consumption of carbapenems (r: 0.8759; P < 0.001 and r: 0.8968; P < 0.001), SXT (r: 0.7552; P = 0.011 and r: 0.7004; P = 0.024), and glycopeptides (r: 0.7542; P = 0.012 and r: 0.8138; P < 0.001) with SM and SXT-resistant SM incidence-density/1000 patient-days, respectively. Implementation of institutional carbapenem-sparing strategies are critical in preserving these life-saving drugs, and may affect the microbial spectrum of infections in clinical settings.

Stenotrophomonas maltophilia Outbreak in an ICU: Investigation of Possible Routes of Transmission and Implementation of Infection Control Measures

Stenotrophomonas maltophilia, a non-fermentative, ubiquitous, gram-negative aerobic bacterium, is associated with high mortality rates, particularly in immunocompromised or debilitated patients. The prevalence rate of ICU-acquired pneumonia episodes caused by this microorganism has been found to be 2%. S. maltophilia has been identified as one of the top 10 microorganisms responsible for such infections in EU/EEA countries. This study describes an outbreak of S. maltophilia in an intensive care unit of a hospital in northern Italy. This includes an epidemiological investigation of the cases, the environmental microbiological controls carried out, a comparison of the strains by multilocus sequence typing (MLST), and the measures taken to prevent and control the outbreak. Among the seven clinical isolates of S. maltophilia analyzed herein, six demonstrated susceptibilities to trimethoprim-sulfamethoxazole. Conversely, one isolate of S. maltophilia exhibited resistance to first-line antibiotics. ST was found to be identical for six patients (ST 4), as well as in the environmental feedback on the trolley of Box 2. The analysis of the temporal and spatial progression of the outbreak has suggested that the transmission of S. maltophilia may have occurred through cross-transmission during care practices.

The airway microbiome of persons with cystic fibrosis correlates with acquisition and microbiological outcomes of incident Stenotrophomonas maltophilia infection

Rationale

Chronic infection with Stenotrophomonas maltophilia in persons with cystic fibrosis (pwCF) has been linked to an increased risk of pulmonary exacerbations and lung function decline. We sought to establish whether baseline sputum microbiome associates with risk of S. maltophilia incident infection and persistence in pwCF.

Methods

pwCF experiencing incident S. maltophilia infections attending the Calgary Adult CF Clinic from 2010-2018 were compared with S. maltophilia-negative sex, age (+/-2 years), and birth-cohort-matched controls. Infection outcomes were classified as persistent (when the pathogen was recovered in ≥50% of cultures in the subsequent year) or transient. We assessed microbial communities from prospectively biobanked sputum using V3-V4 16S ribosomal RNA (rRNA) gene sequencing, in the year preceding (Pre) (n = 57), at (At) (n = 22), and after (Post) (n = 31) incident infection. We verified relative abundance data using S. maltophilia-specific qPCR and 16S rRNA-targeted qPCR to assess bioburden. Strains were typed using pulse-field gel electrophoresis.

Results

Twenty-five pwCF with incident S. maltophilia (56% female, median 29 years, median FEV1 61%) with 33 total episodes were compared with 56 uninfected pwCF controls. Demographics and clinical characteristics were similar between cohorts. Among those with incident S. maltophilia infection, sputum communities did not cluster based on infection timeline (Pre, At, Post). Communities differed between the infection cohort and controls (n = 56) based on Shannon Diversity Index (SDI, p = 0.04) and clustered based on Aitchison distance (PERMANOVA, p = 0.01) prior to infection. At the time of incident S. maltophilia isolation, communities did not differ in SDI but clustered based on Aitchison distance (PERMANOVA, p = 0.03) in those that ultimately developed persistent infection versus those that were transient. S. maltophilia abundance within sputum was increased in samples from patients (Pre) relative to controls, measuring both relative (p = 0.004) and absolute (p = 0.001). Furthermore, S. maltophilia abundance was increased in sputum at incident infection in those who ultimately developed persistent infection relative to those with transient infection, measured relatively (p = 0.04) or absolute (p = 0.04), respectively.

Conclusion

Microbial community composition of CF sputum associates with S. maltophilia infection acquisition as well as infection outcome. Our study suggests sputum microbiome may serve as a surrogate for identifying infection risk and persistence risk.

Novel case of combination antibiotic therapy for treatment of a complicated polymicrobial urinary tract infection with one organism harboring a metallo-β-lactamase (MBL) in a pregnant patient

Carbapenem resistance due to metallo-beta-lactamases (MBLs) is a global phenomenon and an important challenge for antibiotic therapy (Boyd et al., 2020 [1]). While previous reports have demonstrated both in vitro and in vivo synergy using the combination of ceftazidime-avibactam and aztreonam against Stenotrophomonas maltophilia, an MBL-harboring organism, this treatment strategy has not been reported during pregnancy (Mojic et al., 2017 [2], [3], Mojica et al., 2016 [4], Alexander et al., 2020 [5]). We describe a 33-year-old pregnant female with polymicrobial, bilateral pyelonephritis caused by Stenotrophomonas maltophilia and other gram-negative bacteria. The organisms were eradicated with the combination of ceftazidime-avibactam and aztreonam followed by successful delivery with no observed adverse effects in either mother or child post-partum.

Global mapping of antibiotic resistance rates among clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

INTRODUCTION

Infections caused by Stenotrophomonas maltophilia are clinically important due to its intrinsic resistance to a broad range of antibiotics. Therefore, selecting the most appropriate antibiotic to treat S. maltophilia infection is a major challenge.

AIM

The current meta-analysis aimed to investigate the global prevalence of antibiotic resistance among S. maltophilia isolates to the develop more effective therapeutic strategies.

METHOD

A systematic literature search was performed using the appropriate search syntax after searching Pubmed, Embase, Web of Science and Scopus databases (May 2023). Statistical analysis was performed using Pooled and the random effects model in R and the metafor package. A total of 11,438 articles were retrieved. After a thorough evaluation, 289 studies were finally eligible for inclusion in this systematic review and meta-analysis.

RESULT

Present analysis indicated that the highest incidences of resistance were associated with doripenem (97%), cefoxitin (96%), imipenem and cefuroxime (95%), ampicillin (94%), ceftriaxone (92%), aztreonam (91%) and meropenem (90%) which resistance to Carbapenems is intrinsic. The lowest resistance rates were documented for minocycline (3%), cefiderocol (4%). The global resistance rate to TMP-SMX remained constant in two periods before and after 2010 (14.4% vs. 14.6%). A significant increase in resistance to tigecycline and ceftolozane/tazobactam was observed before and after 2010.

CONCLUSIONS

Minocycline and cefiderocol can be considered the preferred treatment options due to low resistance rates, although regional differences in resistance rates to other antibiotics should be considered. The low global prevalence of resistance to TMP-SMX as a first-line treatment for S. maltophilia suggests that it remains an effective treatment option.

Emerging importance of multidrug-resistant Stenotrophomonas maltophilia infections in neonatal intensive care unit in a tertiary center in Turkey

OBJECTIVE

Stenotrophomonas maltophilia is an emerging multi-drug resistant, opportunistic pathogen in the neonatal intensive care unit (NICU). In this study, we aimed to assess the incidence, clinical features, antibiotic susceptibility, and treatment options of S. maltophilia infection among the healthcare-associated infections (HAIs) in the neonatal unit.

METHODS

In this study, the patients who were hospitalized in the NICU between January 2020 and December 2021 with S. maltophilia isolated from clinical samples were included. Demographic, clinic features, and microbiological findings of the patients were retrospectively evaluated by using the medical records. The samples (lower respiratory tract, urine, peritoneal fluid) were first examined microscopically by gram preparation and cultured. Antibiotic susceptibility tests were performed according to the recommendations of The European Committee on Antimicrobial Susceptibility Testing (EUCAST) for TMP-SMX.

RESULTS

S. maltophilia was isolated in 38 clinical samples of the 20 patients who were hospitalized at the NICU between January 2020 and December 2021. A total of 40 % (n = 8) of samples from different patients were accepted as colonization. Ventilator-associated pneumonia was determined in 55 % (n = 11), and urinary tract infection in 5 % (n = 1). S. maltophilia-associated bacteremia was not detected in any of the cases. The TMP-SMX susceptibilities of the strains were as it follows: 3 (15 %) were resistant (R), 7 (28 %) were susceptible (S), and 10 (47 %) were susceptible-increased exposure (I). Three of these patients were given dual antibiotics therapy (levofloxacin plus TMP-SMX) and nine of them were given only TMP-SMX. The most common hospital-acquired infectious agents are Gram negative microorganisms (51 %), followed by coagulase negative staphylococci (CNS), Staphylococcus aureus (24 %) and S. maltophilia (24 %).

CONCLUSION

Increasing TMP-SMX resistance and specific drug and dosage-related problems in the neonatal unit are important problems in treatment management.

Stenotrophomonas maltophilia Infections in Haematological Malignancies and Hematopoietic Stem Cell Transplantation: A Case Series including Cefiderocol-Based Regimens

Background and Objectives: Stenotrophomonas maltophilia is a ubiquitous, aerobic, Gram-negative bacillus causing increasing concern in patients affected by haematological malignancies. Materials and Methods: We report a case series from two centres in Northern Italy to describe the characteristics, outcome and microbiological response of S. maltophilia infections in patients with haematological malignancies and/or allogenic hematopoietic stem cell transplantation (aHSCT). Results: Ten patients were included. The median age was 67 years, and seven patients (70%) were males. The median Charlson Comorbidity Index was 6 (IQR: 4-8). The most frequent haematological comorbidities were acute myeloid leukaemia (AML; n = 3; 30%) and non-Hodgkin's lymphoma (n = 3; 30%). Three (30%) patients underwent aHSCT before infection, all for AML. All the patients had undergone a recent antibiotics course and had an indwelling central venous catheter before infection. The main clinical presentations were nosocomial pneumonia, with (2; 20%) or without (4; 40%) secondary bloodstream infection and CRBSI (3; 30%). Four patients were treated with cefiderocol in monotherapy or combinations therapy with cotrimoxazole. The rest of the patients were treated with cotrimoxazole or levofloxacin in monotherapy. Conclusions: Despite a high rate of clinical improvement (90%) after starting antimicrobial therapy, we faced high 30-day mortality (30%) and in-hospital mortality (50%) rates in a highly comorbid population.

Emerging infections in vulnerable hosts: Stenotrophomonas maltophilia and Elizabethkingia anophelis

PURPOSE OF REVIEW

This systematic review aimed to explore the recent trends in the epidemiology, risk factors, and antimicrobial susceptibility of two emerging opportunistic pathogens, Stenotrophomonas maltophilia and Elizabethkingia anophelis .

RECENT FINDINGS

Since 2020, numerous outbreaks of S. maltophilia and E. anophelis have been reported worldwide. Most of these outbreaks have been associated with healthcare facilities, although one outbreak caused by E. anophelis in France was considered a community-associated infection. In terms of antimicrobial susceptibility, trimethoprim/sulfamethoxazole (TMP-SMZ), levofloxacin, and minocycline have exhibited good efficacy against S. maltophilia . Additionally, cefiderocol and a combination of aztreonam and avibactam have shown promising results in in vitro susceptibility testing. For E. anophelis , there is currently no consensus on the optimal treatment. Although some studies have reported good efficacy with rifampin, TMP-SMZ, piperacillin/tazobactam, and cefoperazone/sulbactam, minocycline had the most favourable in vitro susceptibility rates. Cefiderocol may serve as an alternative due to its low minimum inhibitory concentration (MIC) against E. anophelis . The role of vancomycin in treatment is still uncertain, although several successful cases with vancomycin treatment, even with high MIC values, have been reported.

SUMMARY

Immunocompromised patients are particularly vulnerable to infections caused by S. maltophilia and E. anophelis , but the optimal treatment strategy remains inconclusive. Further research is necessary to determine the most effective use of conventional and novel antimicrobial agents in combatting these multidrug-resistant pathogens.

Editorial for the Special Issue: "The Issue of Multidrug-Resistant Pathogens in Nosocomial Infections"

Antimicrobial resistance (AMR) is a global problem; in 2019, before the Coronavirus Disease 2019 (COVID-19) pandemic, it was responsible of more deaths than any other infectious diseases, including human immunodeficiency virus and malaria [...].

Stenotrophomonas maltophilia: An Urgent Threat with Increasing Antibiotic Resistance

Stenotrophomonas maltophilia is a Gram-negative opportunistic pathogen that can cause many infections, such as chronic pulmonary infections in patients with cystic fibrosis and infections in immunocompromised patients with hematology-oncology diseases. Because of its remarkable and increasing antimicrobial resistance, the treatment of S. maltophilia infections is quite challenging. Meanwhile, the prevalence of S. maltophilia infections is increasing in recent decades. S. maltophilia is usually considered to be of low virulence but has numerous virulence factors involved in the pathogenesis of infections caused by S. maltophilia. By revealing its pathogenesis associated with virulence factors and molecular mechanisms of antimicrobial resistance, many existing or potential therapeutic strategies have been developed. However, because of the limited treatment options, new strategies are urgently needed. Here, we review the recent progresses in research on S. maltophilia which may help to develop more effective treatments against this increasing threat.

Risk factors for mortality in intensive care unit patients with Stenotrophomonas maltophilia pneumonia in South Korea

BACKGROUND

Stenotrophomonas maltophilia has been increasingly recognized as an opportunistic pathogen associated with high morbidity and mortality. Data on the prognostic factors associated with S. maltophilia pneumonia in patients admitted to intensive care unit (ICU) are lacking.

METHODS

We conducted a retrospective analysis of data from 117 patients with S. maltophilia pneumonia admitted to the ICUs of two tertiary referral hospitals in South Korea between January 2011 and December 2022. To assess risk factors associated with in-hospital mortality, multivariable logistic regression analyses were performed.

RESULTS

The median age of the study population was 71 years. Ventilator-associated pneumonia was 76.1% of cases, and the median length of ICU stay before the first isolation of S. maltophilia was 15 days. The overall in-hospital mortality rate was 82.1%, and factors independently associated with mortality were age (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.00-1.09; P=0.046), Sequential Organ Failure Assessment (SOFA) score (OR, 1.21; 95%; CI, 1.02-1.43; P=0.025), corticosteroid use (OR, 4.19; 95% CI, 1.26-13.91; P=0.019), and polymicrobial infection (OR, 95% CI 0.07-0.69). However, the impact of appropriate antibiotic therapy on mortality was insignificant. In a subgroup of patients who received appropriate antibiotic therapy (n=58), antibiotic treatment modality-related variables, including combination or empirical therapy, also showed no significant association with survival.

CONCLUSIONS

Patients with S. maltophilia pneumonia in ICU have high mortality rates. Older age, higher SOFA score, and corticosteroid use were independently associated with increased in-hospital mortality, whereas polymicrobial infection was associated with lower mortality. The effect of appropriate antibiotic therapy on prognosis was insignificant.

Diversity of blaL1-like genes in Stenotrophomonas species: insights from genome analysis of publicly available genome sequences

L1 metallo-β-lactamases produced by Stenotrophomonas maltophilia exhibit high diversity. Here, we characterized the genomes of Stenotrophomonas species harboring blaL1-like genes using publicly available genome sequences. Our findings provide evidence that Stenotrophomonas species with blaL1-like genes constitute a complex comprising many species with high genetic diversity, and similarities between blaL1-like genes are lower than those of the genome. This suggests that the diversity of blaL1-like is attributable to species diversity in Stenotrophomonas species harboring blaL1-like and the rapid evolutionary changes in blaL1-like genes.

Inhalable Excipient-Free Dry Powder of Tigecycline for the Treatment of Pulmonary Infections

Tigecycline (TIG) is a broad-spectrum antibiotic that has been approved for the treatment of a number of complicated infections, including community-acquired bacterial pneumonia. Currently it is available only as an intravenous injection that undergoes rapid chemical degradation and limits the use to in-patient scenarios. The use of TIG as an inhaled dry powder inhaler may offer a promising treatment option for patients with multidrug-resistant respiratory tract infections, such as Stenotrophomonas maltophilia (S. maltophilia). This study explores the feasibility of engineering an inhaled powder formulation of TIG that could administer relevant doses at a wide range of inhalation flow rates while maintaining stability of this labile drug. Using air-jet milling, micronized TIG had excellent aerosolization efficiency, with over 80% of the device emitted dose being within the respirable range. TIG was also readily dispersed using different inhaler devices even when tested at different pressure drops and flow rates. Additionally, micronized TIG was stable for 6 months at 25 °C/60% RH and 40 °C/75% RH. Micronized TIG maintained a low minimum inhibitory concentration (MIC) and minimum biofilm eradication concentration (MBEC) of 0.8 μM and >0.5 μM, respectively in S. maltophilia cultures in vitro. These results strongly suggest that the micronization of TIG results in a stable and respirable formulation that can be delivered via the pulmonary route for the treatment of lung infections.

Global prevalence and distribution of antibiotic resistance among clinical isolates of Stenotrophomonas maltophilia: A systematic review and meta-analysis

OBJECTIVES

Stenotrophomonas maltophilia (S. maltophilia), an opportunistic pathogen, causes infection in patients undergoing immunosuppressive therapy, mechanical ventilation, or catheters and in long-term hospitalized patients. Due to its extensive resistance to various antibiotics and chemotherapeutic agents, S. maltophilia is challenging to treat. Using case reports, case series, and prevalence studies, the current study provides a systematic review and meta-analysis of antibiotic resistance profiles across clinical isolates of S. maltophilia.

METHODS

A systematic literature search was performed for original research articles published in Medline, Web of Science, and Embase databases from 2000 to 2022. Statistical analysis was performed using STATA 14 software to report antibiotic resistance of S. maltophilia clinical isolates worldwide.

RESULTS

223 studies (39 case reports/case series and 184 prevalence studies) were collected for analysis. A meta-analysis of prevalence studies demonstrated that the most antibiotic resistance worldwide was to levofloxacin, trimethoprim-sulfamethoxazole (TMP/SMX), and minocycline (14.4%, 9.2%, and 1.4%, respectively). Resistance to TMP/SMX (36.84%), levofloxacin (19.29%), and minocycline (1.75%) were the most prevalent antibiotic resistance types found in evaluated case reports/case series studies. The highest resistance rate to TMP/SMX was reported in Asia (19.29%), Europe (10.52%), and America (7.01%), respectively.

CONCLUSION

Considering the high resistance to TMP/SMX, more attention should be paid to patients' drug regimens to prevent the emergence of multidrug-resistant S. maltophilia isolates.

Antibiotic potentiation and inhibition of cross-resistance in pathogens associated with cystic fibrosis

Critical Gram-negative pathogens, like Pseudomonas, Stenotrophomonas and Burkholderia, have become resistant to most antibiotics. Complex resistance profiles together with synergistic interactions between these organisms increase the likelihood of treatment failure in distinct infection settings, for example in the lungs of cystic fibrosis patients. Here, we discover that cell envelope protein homeostasis pathways underpin both antibiotic resistance and cross-protection in CF-associated bacteria. We find that inhibition of oxidative protein folding inactivates multiple species-specific resistance proteins. Using this strategy, we sensitize multi-drug resistant Pseudomonas aeruginosa to β-lactam antibiotics and demonstrate promise of new treatment avenues for the recalcitrant pathogen Stenotrophomonas maltophilia. The same approach also inhibits cross-protection between resistant S. maltophilia and susceptible P. aeruginosa, allowing eradication of both commonly co-occurring CF-associated organisms. Our results provide the basis for the development of next-generation strategies that target antibiotic resistance, while also impairing specific interbacterial interactions that enhance the severity of polymicrobial infections.

Steno-sphere: Navigating the enigmatic world of emerging multidrug-resistant Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is an opportunistic pathogen and frequent cause of serious nosocomial infections. Patient populations at greatest risk for these infections include the immunocompromised and those with chronic respiratory illnesses and prior antibiotic exposure, notably to carbapenems. Its complex virulence and resistance profile drastically limit available antibiotics, and incomplete breakpoint and pharmacokinetic/pharmacodynamic (PK/PD) data to inform dose optimization further complicates therapeutic approaches. Clinical comparison data of first-line agents, including trimethoprim-sulfamethoxazole (TMP-SMX), quinolones, and minocycline, are limited to conflicting observational data with no clear benefit of a single agent or combination therapy. Newer antibiotic approaches, including cefiderocol and aztreonam- avibactam, are promising alternatives for extensively drug-resistant isolates; however, clinical outcomes data are needed. The potential clinical utility of bacteriophage for compassionate use in treating S. maltophilia infections remains to be determined since data is limited to in-vitro and sparse in-vivo work. This article provides a review of available literature for S. maltophilia infection management focused on related epidemiology, resistance mechanisms, identification, susceptibility testing, antimicrobial PK/PD, and emerging therapeutic strategies.

The prevalence of colistin resistance in clinical Stenotrophomonas maltophilia isolates worldwide: a systematic review and meta-analysis

While trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line therapy of Stenotrophomonas maltophilia infections, colistin is one of the therapeutic options in cases of allergy or resistance to TMP-SMX. However, understanding the global status of resistance to colistin amongst S. maltophilia isolates could be helpful for appropriate antibiotic prescription. This study aimed to conduct a systematic review and meta-analysis to examine the prevalence of colistin resistance in clinical S. maltophilia isolates worldwide. According to eligibility criteria, a total of 61 studies were included in the analysis. The pooled prevalence for colistin resistance was 42% (95% CI: 35-49%), ranging from 0.1 to 97%. Subgroups analysis indicated that, the pooled prevalence of colistin resistance was 44% (95% CI: 29-60%) in 15 studies during 2000-2010, and it was estimated to be 41% (95% CI: 33-50%) in 46 articles from 2011 to 2021. It was 46% (95% CI: 35-58%) in the studies that used broth microdilution method, and 39% (95% CI: 30-49%) in the studies with other used methods. The resistance rate in Asian countries was 45% (95% CI: 31-60%), in European countries was 45% (95% CI: 34-56%) and in the countries of North and South America was 33% (95% CI: 20-46%). Our review showed notable resistance to colistin in clinical S. maltophilia isolates. Given the estimated resistance rates, alternative antibiotics could be preferred to treat serious infections due to S. maltophilia.

In vitro activities of antimicrobial combinations against planktonic and biofilm forms of Stenotrophomonas maltophilia

Objectives

To investigate the in vitro activity of antibiotic combinations against Stenotrophomonas maltophilia isolates and their associated biofilms.

Methods

Thirty-two S. maltophilia clinical isolates with at least twenty-five different pulsotypes were tested. The antibacterial activity of various antibiotic combinations against seven randomly selected planktonic and biofilm-embedded S. maltophilia strains with strong biofilm formation was assessed using broth methods. Extraction of bacterial genomic DNA and PCR detection of antibiotic resistance and biofilm-related genes were also performed.

Results

The susceptibility rates of levofloxacin (LVX), fosfomycin (FOS), tigecycline (TGC) and sulfamethoxazole-trimethoprim (SXT) against 32 S. maltophilia isolates were 56.3, 71.9, 71.9 and 90.6%, respectively. Twenty-eight isolates were detected with strong biofilm formation. Antibiotic combinations, including aztreonam-clavulanic (ATM-CLA) with LVX, ceftazidime-avibactam (CZA) with LVX and SXT with TGC, exhibited potent inhibitory activity against these isolates with strong biofilm formation. The antibiotic resistance phenotype might not be fully caused by the common antibiotic-resistance or biofilm-formation gene.

Conclusion

S. maltophilia remained resistant to most antibiotics, including LVX and β-lactam/β-lactamases; however, TGC, FOS and SXT still exhibited potent activity. Although all tested S. maltophilia isolates exhibited moderate-to-strong biofilm formation, combination therapies, especially ATM-CLA with LVX, CZA with LVX and SXT with TGC, exhibited a higher inhibitory activity for these isolates.

Stenotrophomonas maltophilia Infections: A Systematic Review and Meta-Analysis of Comparative Efficacy of Available Treatments, with Critical Assessment of Novel Therapeutic Options

Stenotrophomonas maltophilia (SM) represents a challenging pathogen due to its resistance profile. A systematic review of the available evidence was conducted to evaluate the best treatment of SM infections to date, focusing on trimethoprim/sulfamethoxazole (TMP/SMX), fluoroquinolones (FQs), and tetracycline derivatives (TDs).

MATERIALS

PubMed/MEDLINE and Embase were searched from inception to 30 November 2022. The primary outcome was all-cause mortality. Secondary outcomes included clinical failure, adverse events, and length of stay. A random effects meta-analysis was performed. This study was registered with PROSPERO (CRD42022321893).

RESULTS

Twenty-four studies, all retrospective, were included. A significant difference in terms of overall mortality was observed when comparing as a monotherapy TMP/SMX versus FQs (odds ratio (OR) 1.46, 95% confidence interval (CI) 1.15-1.86, I² = 33%; 11 studies, 2407 patients). The prediction interval (PI) did not touch the no effect line (1.06-1.93), but the results were not robust for the unmeasured confounding (E-value for point estimate of 1.71). When comparing TMP/SMX with TDs, the former showed an association with higher mortality but not significant and with a wide PI (OR 1.95, 95% CI 0.79-4.82, PI 0.01-685.99, I² = 0%; 3 studies, 346 patients). Monotherapies in general exerted a protective effect against death opposed to the combination regimens but were not significant (OR 0.71, 95% CI 0.41-1.22, PI 0.16-3.08, I² = 0%; 4 studies, 438 patients).

CONCLUSIONS

Against SM infections, FQs and, possibly, TDs seem to be reasonable alternative choices to TMP/SMX. Data from clinical trials are urgently needed to better inform therapeutic choices in this setting by also taking into account newer agents.

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Expanding therapeutic potential of Bdellovibrio bacteriovorus against multidrug-resistant pathogens

Novel treatments toward Gram-negative bacteria are urgently needed to prevent even higher mortality levels associated with resistant bacterial infections. Predatory bacteria have been studied as a new type of treatment against pathogenic bacteria, including resistant species. However, because of limitations related to eradication efficacy, combination therapy using predatory bacteria with other agents has also been tested. Here, we discuss recent advances in the use of predatory bacteria to treat infections and propose novel combinatory strategies with antivirulence compounds. Teaser: The increasing number of resistant bacteria requires the implementation of new strategies to avoid mortality. Studies about predatory bacteria indicate a field to be explored in different ways that can lead to new treatment solutions.

Upraising Stenotrophomonas maltophilia in Critically Ill Patients: A New Enemy?

Stenotrophomonas maltophilia (S. maltophilia), an important pathogen in immuno-compromised patients, has recently gained attention in patients admitted in intensive care units (ICU). We sought to investigate clinical features of infections caused by S. maltophilia in ICU patients and identify risk factors for mortality. We conducted a retrospective study in two multivalent non-COVID-19 ICUs of tertiary-teaching hospitals in Greece and Spain, including patients with isolated S. maltophilia from at least one clinical specimen along with clinical signs of infection. A total of 103 patients (66% male) were analyzed. Median age was 65.5 (54–73.3) years and mean APACHE II and SOFA scores upon ICU admission were 18.36 (±7.22) and 18.17 (±6.95), respectively. Pneumonia was the predominant clinical syndrome (72.8%), while 22% of cases were among hemato/oncology patients. Crude 28-day mortality rate was 54.8%, even though, 14-day clinical and microbiological response was 96%. Age, APACHE II on ICU admission, hemato-oncologic disease, and multi-organ failure were initially identified as potential predictors of mortality. In the multivariable analysis, only increasing age and hemato-oncologic disease were shown to be independent risk factors for 28-day mortality. High all-cause mortality was observed in critically ill patients with predominantly respiratory infections by S. maltophilia, despite initial clinical and laboratory response after targeted treatment. The study elucidates a potentially worrisome emerging pathogen in the ICU.

Genotypic Diversity, Antibiotic Resistance, and Virulence Phenotypes of Stenotrophomonas maltophilia Clinical Isolates from a Thai University Hospital Setting

Stenotrophomonas maltophilia is a multidrug-resistant organism that is emerging as an important opportunistic pathogen. Despite this, information on the epidemiology and characteristics of this bacterium, especially in Thailand, is rarely found. This study aimed to determine the demographic, genotypic, and phenotypic characteristics of S. maltophilia isolates from Maharaj Nakorn Chiang Mai Hospital, Thailand. A total of 200 S. maltophilia isolates were collected from four types of clinical specimens from 2015 to 2016 and most of the isolates were from sputum. In terms of clinical characteristics, male and aged patients were more susceptible to an S. maltophilia infection. The majority of included patients had underlying diseases and were hospitalized with associated invasive procedures. The antimicrobial resistance profiles of S. maltophilia isolates showed the highest frequency of resistance to ceftazidime and the lower frequency of resistance to chloramphenicol, levofloxacin, trimethoprim/sulfamethoxazole (TMP/SMX), and no resistance to minocycline. The predominant antibiotic resistance genes among the 200 isolates were the smeF gene (91.5%), followed by bla_L1 and bla_L2 genes (43% and 10%), respectively. Other antibiotic resistance genes detected were floR (8.5%), intI1 (7%), sul1 (6%), mfsA (4%) and sul2 (2%). Most S. maltophilia isolates could produce biofilm and could swim in a semisolid medium, however, none of the isolates could swarm. All isolates were positive for hemolysin production, whereas 91.5% and 22.5% of isolates could release protease and lipase enzymes, respectively. In MLST analysis, a high degree of genetic diversity was observed among the 200 S. maltophilia isolates. One hundred and forty-one sequence types (STs), including 130 novel STs, were identified and categorized into six different clonal complex groups. The differences in drug resistance patterns and genetic profiles exhibited various phenotypes of biofilm formation, motility, toxin, and enzymes production which support this bacterium in its virulence and pathogenicity. This study reviewed the characteristics of genotypes and phenotypes of S. maltophilia from Thailand which is necessary for the control and prevention of S. maltophilia local spreading.

Prevalence and Characterization of Beta-Lactam and Carbapenem-Resistant Bacteria Isolated from Organic Fresh Produce Retailed in Eastern Spain

Fresh fruits and vegetables are potential reservoirs for antimicrobial resistance determinants, but few studies have focused specifically on organic vegetables. The present study aimed to determine the presence of third-generation cephalosporin (3GC)- and carbapenem-resistant Gram-negative bacteria on fresh organic vegetables produced in the city of Valencia (Spain). Main expanded spectrum beta-lactamase (ESBL)- and carbapenemase-encoding genes were also detected in the isolates. One hundred and fifteen samples were analyzed using selective media supplemented with cefotaxime and meropenem. Resistance assays for twelve relevant antibiotics in medical use were performed using a disc diffusion test. A total of 161 isolates were tested. Overall, 33.5% presented multidrug resistance and 16.8% were resistant to all β-lactam antibiotics tested. Imipenem resistance was observed in 18% of isolates, and low resistance levels were found to ceftazidime and meropenem. Opportunistic pathogens such as Acinetobacter baumannii, Enterobacter spp., Raoultella sp., and Stenotrophomonas maltophilia were detected, all presenting high rates of resistance. PCR assays revealed bla_VIM to be the most frequently isolated ESBL-encoding gene, followed by bla_TEM and bla_OXA-48. These results confirm the potential of fresh vegetables to act as reservoirs for 3GC- and carbapenem-producing ARB. Further studies must be carried out to determine the impact of raw organic food on the spread of AMRs into the community.

Antibiofilm and antimicrobial activity of curcumin-chitosan nanocomplexes and trimethoprim-sulfamethoxazole on Achromobacter, Burkholderia, and Stenotrophomonas isolates

BACKGROUND

Non-fermenting Gram-negative Achromobacter xylosoxidans, Burkholderia cepacia complex, and Stenotrophomonas maltophilia species cause healthcare-associated infections, often showing resistance to first-line drugs such as trimethoprim-sulfamethoxazole (TMP-SXT). The aim of this study was to determine the effect of curcumin-chitosan nanocomplexes on biofilm-producing clinical isolates of non-fermenting Gram-negative bacilli.

METHODS

A. xylosoxidans, B. cepacia complex, and S. maltophilia clinical isolates were identified by MALDI-TOF mass spectrometry. Antimicrobial susceptibility was determined by broth microdilution. Curcumin (Cur), chitosan (Chi), and sodium tripolyphosphate (TPP) were encapsulated by ionotropic gelation in magnetic nanoparticles (MNP) and were assessed by scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR). Biofilm inhibition and eradication by Cur-Chi-TPP-MNP with TMP-SXT was assessed.

RESULTS

Cur-Chi-TPP-MNP in combination with TMP-SXT showed biofilm inhibition activity in A. xylosoxidans (37.5 µg/mL), B. cepacia (18.75 µg/mL), and S. maltophilia (4.69-18.75 µg/mL) and low biofilm eradication activity in all three strains (150 - 300 µg/mL).

CONCLUSIONS

Cur-Chi-TPP-MNP in combination with TMP-SXT was able to inhibit biofilm and in lower effect to eradicate established biofilms of clinical isolates of A. xylosoxidans, B. cepacia complex, and S. maltophilia species. Our results highlight the need to assess these potential treatment options to be used clinically in biofilm-associated infections.

Risk factors of lower respiratory tract infection caused by Stenotrophomonas maltophilia: Systematic review and meta-analysis

Objective

To systematically evaluate the risk factors of lower respiratory tract infection caused by Stenotrophomonas maltophilia for better clinical treatment.

Methods

PubMed, Embase, the Cochrane Library, Web of Science, China Journal full-text Database (CNKI), Wanfang Database (WanFang Data), VIP (VIP), and China Biomedical Literature Database (CBM) were selected and published by June 2022 about the risk factors of lower respiratory tract infection of S. maltophilia. Two researchers independently screened the literature, extracted data, and quality evaluation according to the inclusion and exclusion criteria. RevMan 5.4 software was used for meta-analysis.

Results

A total of 18 articles were included, including 10 in English and 8 in Chinese. Meta analysis showed that the risk factors of lower respiratory tract infection caused by S. maltophilia included disease severity, hospitalization days, use of glucocorticoids, invasive procedures, use of broad-spectrum antibiotics and use of more than 3 Antibiotics. The OR values of patients with hospitalization, mechanical ventilation, use of more than 3 Antibiotics, endotracheal intubation and tracheotomy were the highest. Specific hospitalization days (OR = 14.56, 95% CI: 6.12~23.01), mechanical ventilation (OR = 14.16, 95% CI: 5.85~34.3), use of more than 3 Antibiotics (OR = 6.21, 95% CI: 1.24~31.14), tracheal intubation (OR = 6.07, 95% CI: 1.97~3.64), tracheotomy (OR = 3.77, 95% CI: 1.09~13.04).

Conclusion

There are many risk factors for lower respiratory tract infection of S. maltophilia, which can occur in patients with severe illness, high APACHE-II score, invasive procedures, and the need for broad-spectrum antibiotics. In terms of the host, these patients are characterized by impaired immune function, severe illness and long-term hospitalization, which objectively leads to the infection of S. maltophilia. Therefore, strengthening the monitoring, prevention and control of patients with risk factors of S. maltophilia infection is conducive to reducing the risk of infection and death.

Risk Factors for Mortality in Patients with Stenotrophomonas maltophilia Bloodstream Infections in Immunocompetent Patients

Objective

This study aimed to evaluate bloodstream infections caused by Stenotrophomonas maltophilia in immunocompetent patients with respect to clinical features and risk factors for mortality.

Methods

We reviewed bloodstream infections detected between January 1, 2012, and July 1, 2021, to identify nosocomial S. maltophilia bacteremia in Koşuyolu Research and Training Hospital.

Results

We identified a total of 97 patients with S. maltophilia bloodstream infections. Of these, 17 patients were excluded because of community-acquired infections (n=9), contamination with S. maltophilia (n=3), and insufficient data (n=5), with 80 (57.5% males) patients remaining for analysis. The source of infection was the respiratory tract in 28 (35%) patients. A central venous catheter was used in 60 (75%) patients, which required replacement in 23 patients within five days after detecting S. maltophilia bacteremia. On antimicrobial susceptibility testing, 71 strains were found to be susceptible and 9 (11.3%) resistant to trimethoprim-sulfamethoxazole. Thirty-day mortality was 33.8%. Non-survivors differed significantly from survivors with respect to higher rates of central venous catheters ( p=0.020), mechanical ventilation (p=0.006), urinary catheters (p=0.021), septic shock (p=0.001), hypoalbuminemia (p=0.026) and thrombocytopenia (p =0.039). S. maltophilia bacteremia was independently associated with mortality in patients with hypoalbuminemia, and replacement of central venous catheters had a protective role in reducing mortality.

Conclusion

As with other bacterial infections, S. maltophilia bacteremia is associated with a considerably high mortality rate in patients with cardiac conditions. The replacement of the catheter seems to play a beneficial role in 30-day survival.

Activity of Delafloxacin and Levofloxacin against Stenotrophomonas maltophilia at Simulated Plasma and Intrapulmonary pH Values

Fluoroquinolones have become a popular treatment option for Stenotrophomonas maltophilia infections. Although levofloxacin is most commonly used, delafloxacin demonstrates comparable in vitro activity when evaluated under standard susceptibility testing conditions at neutral pH. At acidic pH, the activity of the anionic delafloxacin is improved, while the activity of the zwitterionic levofloxacin is reduced. Because the human respiratory tract has a pH of ~6.6 and is the most common site of S. maltophilia infection, it is vital to understand the activity of these agents in this environment. Therefore, levofloxacin and delafloxacin were tested against clinical S. maltophilia isolates via broth microdilution testing (n = 37) and time-kill analysis (n = 5) in neutral cation-adjusted Mueller-Hinton broth (CAMHB) (pH 7.3) and acidic CAMHB (aCAMHB) (pH 6.5). In CAMHB, MIC50 values were similar between levofloxacin and delafloxacin (8 mg/L versus 8 mg/L). In aCAMHB, levofloxacin MICs did not change, while delafloxacin MICs decreased by a median of 4 log2 dilutions (MIC50 values of 8 mg/L versus 0.25 mg/L). In time-kill analyses, levofloxacin and delafloxacin at the maximum drug concentration for the free drug (fCmax) were bactericidal against 3 and 2 isolates in CAMHB, respectively. In aCAMHB, levofloxacin was not bactericidal against any isolate, while delafloxacin was bactericidal against the same 2 isolates. Relative to CAMHB, levofloxacin activity was reduced by 2.5 log10 CFU/mL in aCAMHB, whereas delafloxacin activity was increased 2.7 log10 CFU/mL. Although the bactericidal activity of levofloxacin against S. maltophilia was attenuated in an acidic environment in this study, the increased potency of delafloxacin at pH 6.5 did not translate into improved bactericidal activity in time-kill analyses, compared to pH 7.3. IMPORTANCE Stenotrophomonas maltophilia most often infects the lungs, where the physiologic environment is naturally slightly acidic (pH ~6.6), compared to most parts of the body (such as the bloodstream), which have neutral pH values (~7.4). Pneumonia due to S. maltophilia is often treated with the antibiotic levofloxacin, despite the activity of levofloxacin being known to be impaired at acidic pH. Unfortunately, currently available methods for susceptibility testing of levofloxacin against S. maltophilia are performed at a neutral pH and therefore may not accurately represent the activity of levofloxacin at the site of infection in the lungs. A similar but newer antibiotic in the same class as levofloxacin, namely, delafloxacin, is not affected by being in an acidic environment and may actually work better at lower pH values. Therefore, the purpose of this study was to investigate whether one drug might be better than the other in this setting by testing each agent's ability to kill S. maltophilia at pH 7.3 and pH 6.5. These findings could then be used to design confirmatory studies that may ultimately impact which drug is given to patients with lung infections due to S. maltophilia.